INGENIEUR
Figure 2 : Sample images showing colour changes during drying at 50 ° C . [ a ] RGB images ; [ b ] Backscattering images . Courtesy : Onwude et al . ( 2018 )
Figure 3 : Schematic representation of carrots being treated by the prototype , while the thermalimaging system monitors carrot surface temperature in real time . Courtesy : Gan-Mor et al . ( 2011 ).
The Vis and NIR regions range from 400 to 750 nm and 750 to 2500 nm , respectively . Vis region spectroscopy is based on electronic transitions of molecules that result in the absorption of light of a matched energy level at a specific wavelength . NIR spectroscopy involves measuring the absorption of light related to the vibrations of molecular bonds , associated primarily with water and the dominant macroconstituents of fresh produce . The acquired spectral data is then processed via mathematical techniques ( multivariate chemometric ), for establishing a quantitative or qualitative relationship with the property or quality parameter ( s ) of interest ( see Figure 4 ).
The fast and non-destructive character of spectroscopy techniques combined with the advanced evolution of multivariate chemometric analysis which has evolved from conventional linear modelling to non-linear modelling and to artificial neural networks , makes it an appealing tool as a PA technology in postharvest handling . A large variety of Vis / NIR spectroscopic instruments have become available , from expensive benchtop instruments to low-cost as well as miniaturised handheld devices .
20 VOL 84 OCTOBER-DECEMBER 2020